Abstract

It is estimated that 2 billion of the world's population are latently infected with Mycobacterium tuberculosis (Mtb) with a resultant 8 - 9 million cases of active tuberculosis (TB) and 1.6 million deaths annually. The tools used for diagnosis of TB have remained largely unchanged since the 1880s when sputum microscopy, Mtb culture on solid media, tuberculin skin testing and chest radiology were initially developed. In 1991 the World Health Assembly set targets to be reached in 2005 for 70% case finding of smear-positive TB, which represents 6 million cases to be identified per annum. A second target was that 80% (5 million) of those identified cases should complete anti-TB treatment. Subsequently the millennium development goals of 2000 set a target of halving the prevalence of TB disease from 300/100 000 to 150/100 000 and deaths from 30/100 000 to 15/100 000 by 2015. While progress toward these targets was being made in countries with established market economies there was a quadrupling of TB incidence between 1990 and 2005 in most African countries. In 2005 the World Health Organization Regional Committee for Africa declared TB an emergency for the African region.

In South Africa in 2005 the WHO estimated that of 284 592 TB cases 270 360 were notified to the national TB control programme, representing a somewhat ambitious reported case finding proportion of 95%. The proportion treated under the directly observed treatment (DOTS) programme is 94%, and HIV prevalence among notified cases was 58% (97.5% confidence interval (CI) 49 - 65%). South Africa is a middle-income country and is relatively well provided with 143 laboratories performing sputum smears, and 18 culture laboratories also capable of performing drug sensitivity testing. Multidrug resistance (MDR) in new TB cases varies between provinces from 0.9% to 3.6%, while MDR is higher among retreatment cases, with prevalence rates varying between 1.8% to 13.7% in different provincial surveys.